﻿// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// This file contains an implementation of an H264 Annex-B video stream parser.

#ifndef MEDIA_FILTERS_H264_PARSER_H_
#define MEDIA_FILTERS_H264_PARSER_H_

#include <stddef.h>
#include <stdint.h>
#include <sys/types.h>

#include <map>
#include <vector>

#include "macros.h"
#include "h264_bit_reader.h"
#include "ranges.h"

using namespace std;

namespace media {
    
    struct SubsampleEntry {
        uint32_t clear_bytes;
        uint32_t cypher_bytes;
    };
    
    // For explanations of each struct and its members, see H.264 specification
    // at http://www.itu.int/rec/T-REC-H.264.
    struct MEDIA_EXPORT H264NALU {
        H264NALU();
        
        enum Type {
            kUnspecified = 0,
            kNonIDRSlice = 1,
            kSliceDataA = 2,
            kSliceDataB = 3,
            kSliceDataC = 4,
            kIDRSlice = 5,
            kSEIMessage = 6,
            kSPS = 7,
            kPPS = 8,
            kAUD = 9,
            kEOSeq = 10,
            kEOStream = 11,
            kFiller = 12,
            kSPSExt = 13,
            kReserved14 = 14,
            kReserved15 = 15,
            kReserved16 = 16,
            kReserved17 = 17,
            kReserved18 = 18,
            kCodedSliceAux = 19,
            kCodedSliceExtension = 20,
        };
        
        // After (without) start code; we don't own the underlying memory
        // and a shallow copy should be made when copying this struct.
        const uint8_t* data;
        off_t size;  // From after start code to start code of next NALU (or EOS).
        
        int nal_ref_idc;
        int nal_unit_type;
    };
    
    enum {
        kH264ScalingList4x4Length = 16,
        kH264ScalingList8x8Length = 64,
    };
    
    struct MEDIA_EXPORT H264SPS {
        H264SPS();
        
        enum H264ProfileIDC {
            kProfileIDCBaseline = 66,
            kProfileIDCConstrainedBaseline = kProfileIDCBaseline,
            kProfileIDCMain = 77,
            kProfileIDScalableBaseline = 83,
            kProfileIDScalableHigh = 86,
            kProfileIDCHigh = 100,
            kProfileIDHigh10 = 110,
            kProfileIDSMultiviewHigh = 118,
            kProfileIDHigh422 = 122,
            kProfileIDStereoHigh = 128,
            kProfileIDHigh444Predictive = 244,
        };
        
        enum AspectRatioIdc {
            kExtendedSar = 255,
        };
        
        enum {
            // Constants for HRD parameters (spec ch. E.2.2).
            kBitRateScaleConstantTerm = 6,  // Equation E-37.
            kCPBSizeScaleConstantTerm = 4,  // Equation E-38.
            kDefaultInitialCPBRemovalDelayLength = 24,
            kDefaultDPBOutputDelayLength = 24,
            kDefaultTimeOffsetLength = 24,
        };
        
        int profile_idc;
        bool constraint_set0_flag;
        bool constraint_set1_flag;
        bool constraint_set2_flag;
        bool constraint_set3_flag;
        bool constraint_set4_flag;
        bool constraint_set5_flag;
        int level_idc;
        int seq_parameter_set_id;
        
        int chroma_format_idc;
        bool separate_colour_plane_flag;
        int bit_depth_luma_minus8;
        int bit_depth_chroma_minus8;
        bool qpprime_y_zero_transform_bypass_flag;
        
        bool seq_scaling_matrix_present_flag;
        int scaling_list4x4[6][kH264ScalingList4x4Length];
        int scaling_list8x8[6][kH264ScalingList8x8Length];
        
        int log2_max_frame_num_minus4;
        int pic_order_cnt_type;
        int log2_max_pic_order_cnt_lsb_minus4;
        bool delta_pic_order_always_zero_flag;
        int offset_for_non_ref_pic;
        int offset_for_top_to_bottom_field;
        int num_ref_frames_in_pic_order_cnt_cycle;
        int expected_delta_per_pic_order_cnt_cycle;  // calculated
        int offset_for_ref_frame[255];
        int max_num_ref_frames;
        bool gaps_in_frame_num_value_allowed_flag;
        int pic_width_in_mbs_minus1;
        int pic_height_in_map_units_minus1;
        bool frame_mbs_only_flag;
        bool mb_adaptive_frame_field_flag;
        bool direct_8x8_inference_flag;
        bool frame_cropping_flag;
        int frame_crop_left_offset;
        int frame_crop_right_offset;
        int frame_crop_top_offset;
        int frame_crop_bottom_offset;
        
        bool vui_parameters_present_flag;
        int sar_width;    // Set to 0 when not specified.
        int sar_height;   // Set to 0 when not specified.
        bool bitstream_restriction_flag;
        int max_num_reorder_frames;
        int max_dec_frame_buffering;
        bool timing_info_present_flag;
        int num_units_in_tick;
        int time_scale;
        bool fixed_frame_rate_flag;
        
        // TODO(posciak): actually parse these instead of ParseAndIgnoreHRDParameters.
        bool nal_hrd_parameters_present_flag;
        int cpb_cnt_minus1;
        int bit_rate_scale;
        int cpb_size_scale;
        int bit_rate_value_minus1[32];
        int cpb_size_value_minus1[32];
        bool cbr_flag[32];
        int initial_cpb_removal_delay_length_minus_1;
        int cpb_removal_delay_length_minus1;
        int dpb_output_delay_length_minus1;
        int time_offset_length;
        
        bool low_delay_hrd_flag;
        
        int chroma_array_type;
    };
    
    struct MEDIA_EXPORT H264PPS {
        H264PPS();
        
        int pic_parameter_set_id;
        int seq_parameter_set_id;
        bool entropy_coding_mode_flag;
        bool bottom_field_pic_order_in_frame_present_flag;
        int num_slice_groups_minus1;
        // TODO(posciak): Slice groups not implemented, could be added at some point.
        int num_ref_idx_l0_default_active_minus1;
        int num_ref_idx_l1_default_active_minus1;
        bool weighted_pred_flag;
        int weighted_bipred_idc;
        int pic_init_qp_minus26;
        int pic_init_qs_minus26;
        int chroma_qp_index_offset;
        bool deblocking_filter_control_present_flag;
        bool constrained_intra_pred_flag;
        bool redundant_pic_cnt_present_flag;
        bool transform_8x8_mode_flag;
        
        bool pic_scaling_matrix_present_flag;
        int scaling_list4x4[6][kH264ScalingList4x4Length];
        int scaling_list8x8[6][kH264ScalingList8x8Length];
        
        int second_chroma_qp_index_offset;
    };
    
    struct MEDIA_EXPORT H264ModificationOfPicNum {
        int modification_of_pic_nums_idc;
        union {
            int abs_diff_pic_num_minus1;
            int long_term_pic_num;
        };
    };
    
    struct MEDIA_EXPORT H264WeightingFactors {
        bool luma_weight_flag;
        bool chroma_weight_flag;
        int luma_weight[32];
        int luma_offset[32];
        int chroma_weight[32][2];
        int chroma_offset[32][2];
    };
    
    struct MEDIA_EXPORT H264DecRefPicMarking {
        int memory_mgmnt_control_operation;
        int difference_of_pic_nums_minus1;
        int long_term_pic_num;
        int long_term_frame_idx;
        int max_long_term_frame_idx_plus1;
    };
    
    struct MEDIA_EXPORT H264SliceHeader {
        H264SliceHeader();
        
        enum {
            kRefListSize = 32,
            kRefListModSize = kRefListSize
        };
        
        enum Type {
            kPSlice = 0,
            kBSlice = 1,
            kISlice = 2,
            kSPSlice = 3,
            kSISlice = 4,
        };
        
        bool IsPSlice() const;
        bool IsBSlice() const;
        bool IsISlice() const;
        bool IsSPSlice() const;
        bool IsSISlice() const;
        
        bool idr_pic_flag;       // from NAL header
        int nal_ref_idc;         // from NAL header
        const uint8_t* nalu_data;  // from NAL header
        off_t nalu_size;         // from NAL header
        off_t header_bit_size;   // calculated
        
        int first_mb_in_slice;
        int slice_type;
        int pic_parameter_set_id;
        int colour_plane_id;  // TODO(posciak): use this!  http://crbug.com/139878
        int frame_num;
        bool field_pic_flag;
        bool bottom_field_flag;
        int idr_pic_id;
        int pic_order_cnt_lsb;
        int delta_pic_order_cnt_bottom;
        int delta_pic_order_cnt0;
        int delta_pic_order_cnt1;
        int redundant_pic_cnt;
        bool direct_spatial_mv_pred_flag;
        
        bool num_ref_idx_active_override_flag;
        int num_ref_idx_l0_active_minus1;
        int num_ref_idx_l1_active_minus1;
        bool ref_pic_list_modification_flag_l0;
        bool ref_pic_list_modification_flag_l1;
        H264ModificationOfPicNum ref_list_l0_modifications[kRefListModSize];
        H264ModificationOfPicNum ref_list_l1_modifications[kRefListModSize];
        
        int luma_log2_weight_denom;
        int chroma_log2_weight_denom;
        
        bool luma_weight_l0_flag;
        bool chroma_weight_l0_flag;
        H264WeightingFactors pred_weight_table_l0;
        
        bool luma_weight_l1_flag;
        bool chroma_weight_l1_flag;
        H264WeightingFactors pred_weight_table_l1;
        
        bool no_output_of_prior_pics_flag;
        bool long_term_reference_flag;
        
        bool adaptive_ref_pic_marking_mode_flag;
        H264DecRefPicMarking ref_pic_marking[kRefListSize];
        
        int cabac_init_idc;
        int slice_qp_delta;
        bool sp_for_switch_flag;
        int slice_qs_delta;
        int disable_deblocking_filter_idc;
        int slice_alpha_c0_offset_div2;
        int slice_beta_offset_div2;
        
        // Calculated.
        // Size in bits of dec_ref_pic_marking() syntax element.
        size_t dec_ref_pic_marking_bit_size;
        size_t pic_order_cnt_bit_size;
    };
    
    struct H264SEIRecoveryPoint {
        int recovery_frame_cnt;
        bool exact_match_flag;
        bool broken_link_flag;
        int changing_slice_group_idc;
    };
    
    struct MEDIA_EXPORT H264SEIMessage {
        H264SEIMessage();
        
        enum Type {
            kSEIRecoveryPoint = 6,
        };
        
        int type;
        int payload_size;
        union {
            // Placeholder; in future more supported types will contribute to more
            // union members here.
            H264SEIRecoveryPoint recovery_point;
        };
    };
    
    // Class to parse an Annex-B H.264 stream,
    // as specified in chapters 7 and Annex B of the H.264 spec.
    class MEDIA_EXPORT H264Parser {
    public:
        enum Result {
            kOk,
            kInvalidStream,      // error in stream
            kUnsupportedStream,  // stream not supported by the parser
            kEOStream,           // end of stream
        };
        
        // Find offset from start of data to next NALU start code
        // and size of found start code (3 or 4 bytes).
        // If no start code is found, offset is pointing to the first unprocessed byte
        // (i.e. the first byte that was not considered as a possible start of a start
        // code) and |*start_code_size| is set to 0.
        // Preconditions:
        // - |data_size| >= 0
        // Postconditions:
        // - |*offset| is between 0 and |data_size| included.
        //   It is strictly less than |data_size| if |data_size| > 0.
        // - |*start_code_size| is either 0, 3 or 4.
        static bool FindStartCode(const uint8_t* data,
                                  off_t data_size,
                                  off_t* offset,
                                  off_t* start_code_size);
        
        // Wrapper for FindStartCode() that skips over start codes that
        // may appear inside of |encrypted_ranges_|.
        // Returns true if a start code was found. Otherwise returns false.
        static bool FindStartCodeInClearRanges(const uint8_t* data,
                                               off_t data_size,
                                               const Ranges<const uint8_t*>& ranges,
                                               off_t* offset,
                                               off_t* start_code_size);
        H264Parser();
        ~H264Parser();
        
        void Reset();
        // Set current stream pointer to |stream| of |stream_size| in bytes,
        // |stream| owned by caller.
        // |subsamples| contains information about what parts of |stream| are
        // encrypted.
        void SetStream(const uint8_t* stream, off_t stream_size);
        void SetEncryptedStream(const uint8_t* stream,
                                off_t stream_size,
                                const std::vector<SubsampleEntry>& subsamples);
        
        // Read the stream to find the next NALU, identify it and return
        // that information in |*nalu|. This advances the stream to the beginning
        // of this NALU, but not past it, so subsequent calls to NALU-specific
        // parsing functions (ParseSPS, etc.)  will parse this NALU.
        // If the caller wishes to skip the current NALU, it can call this function
        // again, instead of any NALU-type specific parse functions below.
        Result AdvanceToNextNALU(H264NALU* nalu);
        
        // NALU-specific parsing functions.
        // These should be called after AdvanceToNextNALU().
        
        // SPSes and PPSes are owned by the parser class and the memory for their
        // structures is managed here, not by the caller, as they are reused
        // across NALUs.
        //
        // Parse an SPS/PPS NALU and save their data in the parser, returning id
        // of the parsed structure in |*pps_id|/|*sps_id|.
        // To get a pointer to a given SPS/PPS structure, use GetSPS()/GetPPS(),
        // passing the returned |*sps_id|/|*pps_id| as parameter.
        // TODO(posciak,fischman): consider replacing returning Result from Parse*()
        // methods with a scoped_ptr and adding an AtEOS() function to check for EOS
        // if Parse*() return NULL.
        Result ParseSPS(int* sps_id);
        Result ParsePPS(int* pps_id);
        
        // Return a pointer to SPS/PPS with given |sps_id|/|pps_id| or NULL if not
        // present.
        const H264SPS* GetSPS(int sps_id) const;
        const H264PPS* GetPPS(int pps_id) const;
        
        // Slice headers and SEI messages are not used across NALUs by the parser
        // and can be discarded after current NALU, so the parser does not store
        // them, nor does it manage their memory.
        // The caller has to provide and manage it instead.
        
        // Parse a slice header, returning it in |*shdr|. |*nalu| must be set to
        // the NALU returned from AdvanceToNextNALU() and corresponding to |*shdr|.
        Result ParseSliceHeader(const H264NALU& nalu, H264SliceHeader* shdr);
        
        // Parse a SEI message, returning it in |*sei_msg|, provided and managed
        // by the caller.
        Result ParseSEI(H264SEIMessage* sei_msg);
        
    private:
        // Move the stream pointer to the beginning of the next NALU,
        // i.e. pointing at the next start code.
        // Return true if a NALU has been found.
        // If a NALU is found:
        // - its size in bytes is returned in |*nalu_size| and includes
        //   the start code as well as the trailing zero bits.
        // - the size in bytes of the start code is returned in |*start_code_size|.
        bool LocateNALU(off_t* nalu_size, off_t* start_code_size);
        
        // Exp-Golomb code parsing as specified in chapter 9.1 of the spec.
        // Read one unsigned exp-Golomb code from the stream and return in |*val|.
        Result ReadUE(int* val);
        
        // Read one signed exp-Golomb code from the stream and return in |*val|.
        Result ReadSE(int* val);
        
        // Parse scaling lists (see spec).
        Result ParseScalingList(int size, int* scaling_list, bool* use_default);
        Result ParseSPSScalingLists(H264SPS* sps);
        Result ParsePPSScalingLists(const H264SPS& sps, H264PPS* pps);
        
        // Parse optional VUI parameters in SPS (see spec).
        Result ParseVUIParameters(H264SPS* sps);
        // Set |hrd_parameters_present| to true only if they are present.
        Result ParseAndIgnoreHRDParameters(bool* hrd_parameters_present);
        
        // Parse reference picture lists' modifications (see spec).
        Result ParseRefPicListModifications(H264SliceHeader* shdr);
        Result ParseRefPicListModification(int num_ref_idx_active_minus1,
                                           H264ModificationOfPicNum* ref_list_mods);
        
        // Parse prediction weight table (see spec).
        Result ParsePredWeightTable(const H264SPS& sps, H264SliceHeader* shdr);
        
        // Parse weighting factors (see spec).
        Result ParseWeightingFactors(int num_ref_idx_active_minus1,
                                     int chroma_array_type,
                                     int luma_log2_weight_denom,
                                     int chroma_log2_weight_denom,
                                     H264WeightingFactors* w_facts);
        
        // Parse decoded reference picture marking information (see spec).
        Result ParseDecRefPicMarking(H264SliceHeader* shdr);
        
        // Pointer to the current NALU in the stream.
        const uint8_t* stream_;
        
        // Bytes left in the stream after the current NALU.
        off_t bytes_left_;
        
        H264BitReader br_;
        
        // PPSes and SPSes stored for future reference.
        typedef std::map<int, H264SPS*> SPSById;
        typedef std::map<int, H264PPS*> PPSById;
        SPSById active_SPSes_;
        PPSById active_PPSes_;
        
        // Ranges of encrypted bytes in the buffer passed to
        // SetEncryptedStream().
        Ranges<const uint8_t*> encrypted_ranges_;
        
        DISALLOW_COPY_AND_ASSIGN(H264Parser);
    };
    
}  // namespace media

#endif  // MEDIA_FILTERS_H264_PARSER_H_
